1. Field
The present invention relates to devices, systems, and processes that adjust throttle characteristics in response to varying operating states of a vehicle.
2. Description of the Related Art
In conventional vehicle systems, a degree of engine throttle opening is typically calculated as a function of a throttle request from a driver. As is known in the art, a throttle is a mechanism by which the flow of a fluid may be obstructed. In a conventional internal combustion engine, the throttle is a valve that regulates the amount of air entering the engine, thereby controlling the amount of fuel burned on each engine cycle as a result of the vehicle's fuel-injector or carburetor maintaining a substantially constant air to fuel ratio. In conventional vehicle systems, the throttle is typically a butterfly valve. In a fuel-injected engine, the throttle valve is housed in the throttle body, whereas in a carbureted engine, the throttle valve is housed in the carburetor.
In a conventional vehicle system, the control used by a driver to regulate engine power may be a throttle pedal (also referred to as an accelerator pedal). A driver can control the degree of opening of the throttle valve by adjusting the degree of depression of the accelerator pedal. When the throttle is completely open, the intake manifold is usually at ambient pressure. On the other hand, when the throttle valve is partially closed, a partial vacuum develops inside the intake manifold as the intake air drops below ambient pressure. The throttle valve may be controlled mechanically through mechanical linkage of the throttle valve and the accelerator pedal. Alternatively, in vehicles with electronic throttle control, opening characteristics of the throttle valve are controlled electronically by the vehicle's electronic control unit (ECU).
As noted above, in conventional vehicle systems, the accelerator pedal may be mechanically linked to the throttle valve to provide mechanical control of the throttle valve opening. Alternatively, in so-called “drive-by-wire” vehicles equipped with electronic throttle control, the accelerator pedal is not mechanically linked to the throttle. Instead, an electronic control unit (ECU) determines the required throttle opening degree based on a mapping to data measured from various sensors including an accelerator pedal position sensor, an engine speed sensor, a vehicle speed sensor, and so forth. In addition, ECUs may use signals generated by a throttle position sensor in a feedback loop to control throttle position. A throttle position sensor is a sensor used to monitor the position of the throttle valve in an engine. The sensor is typically located on the butterfly spindle of the throttle valve and is typically a potentiometer that provides a variable resistance that depends on the position of the throttle valve.
As discussed above, in conventional vehicle systems, throttle opening degree is typically a function of the throttle request of a driver (i.e. the displacement of the accelerator pedal). For a given engine speed, the throttle opening degree will increase as the throttle request increases. As engine speed increases, the throttle opening degree will generally increase for a given throttle request amount.
Some conventional vehicle systems also include sensor(s) for determining a longitudinal or transverse angle of inclination of a vehicle. For example, two or more sensors may be disposed in the fuel tank of a vehicle to determine the inclination of a vehicle based on differences in fill height that are detected by the sensors at the same point in time. The arrangement of the sensors may be modified so as to provide a measure of one or both of the longitudinal and transverse inclinations of the vehicle.
In addition, an acceleration sensor may be used to determine the longitudinal inclination of a vehicle. The acceleration sensor may operate by detecting actual vehicle acceleration in terms of absolute amounts of acceleration. In particular, the longitudinal inclination of a vehicle may be determined based on a time profile of acceleration values in combination with another operational quantity such as wheel rpm of the vehicle. An acceleration sensor can detect acceleration even when a vehicle is in a stationary state on an uphill or downhill slope as a result of the component of the gravitational force on the vehicle in the incline direction.
Adjusting torque transmission characteristics based, at least in part, on a signal generated by an acceleration sensor(s) is known in the art. For example, lowering the clutch disengagement threshold to slightly above the idling rpm rate when it is detected that the vehicle is traveling on a downhill slope in order to increase the time period during which the engine rpm and the transmission rpm run synchronously and to prevent repeated engagement and disengagement of the clutch is known in the art.
Also known in the art, is an apparatus and method that compensates for road gradient for more accurate control of an autonomous traveling vehicle. The method involves first detecting a position and speed of a vehicle based on detection signals received from magnetic sensors disposed on the vehicle that communicate with magnetic nails disposed at regular intervals on the road surface. A longitudinal acceleration of the vehicle is then acquired from a longitudinal sensor and is corrected on the basis of data indicative of the slope of the road received from a communication means. A predicted position and speed of the vehicle after T seconds are then calculated based on the information regarding the current position, speed, and acceleration of the vehicle.
Then, a target position and speed after T seconds based on a control plan of the vehicle are determined and the predicted position and speed after T seconds are subtracted from the target position and speed, respectively, to determine a positional error and a speed error. The positional error and the speed error are then multiplied by acceleration control gains to arrive at a target acceleration for the vehicle. However, the acceleration control gains are set assuming that the vehicle is traveling on a flat road. Therefore, the method corrects the target acceleration on the basis of the data indicative of the slope of the road such that the inclination of the road is compensated for and the speed of the vehicle agrees with the vehicle control command.
Also known in the art is an apparatus and method for controlling longitudinal dynamics of a vehicle. The method involves generating a drive train actuating signal that is generated as a function of input data comprising the current driving state of the vehicle and the desired longitudinal speed or acceleration. The apparatus includes a series of controllers that receive various inputs. In particular, a first controller receives a predefined longitudinal desired value that may be representative of either a longitudinal speed or a longitudinal acceleration. The first controller then generates a controller-internal desired driving speed and longitudinal acceleration based on the predefined longitudinal desired value and various information received from a sensor system. These values are supplied to a second controller. The second controller then generates a drive train actuating signal based on the values received from the first controller and the information received from the sensor system. This system is supplied to a drive train actuating element. The information supplied to both controllers from the sensor system may include variables representing current longitudinal acceleration and highway slope.
Various other apparatuses and methods are known in the art for compensating for changes in road gradient that produce changes in engine load and acceleration conditions. For example, various speed control mechanisms (also known as “cruise control” mechanisms) have been proposed that select the greater of a first desired vehicle acceleration based on a driver command and a second desired vehicle acceleration based on a speed control strategy and control the powertrain so that an actual vehicle acceleration approaches the desired vehicle acceleration. Such a speed control mechanism automatically reduces engine torque or the transmission of engine torque to the wheels when the vehicle is traveling downhill in order to maintain a constant speed, or automatically increases engine torque or transmission of engine torque to the wheels when the vehicle is traveling uphill or the driver demands greater acceleration.
In addition, a microprocessor-based control for maintaining vehicle speed as the vehicle encounters changes in road gradient is known in the art. The control first evaluates whether certain conditions are satisfied (e.g. whether the vehicle has experienced a deceleration exceeding a certain threshold, whether the vehicle speed is within a certain predefined range, and whether the vehicle's brakes are being applied by the driver). If these various conditions are satisfied, it is determined that the vehicle is being subjected to an increased load caused, for example, by an increase in road gradient, and the engine operation moves to a higher horsepower v. speed curve, thereby increasing the engine torque output. This allows the vehicle to maintain its speed as the road gradient increases.
Also known in the art is a system and method for adjusting an ordinary target driving force to compensate for increases in running resistance of a vehicle from the standard running resistance.
Although various types of sensors are known in the art for determining the inclination angle of a vehicle, employing a determination of the longitudinal angle of a vehicle to improve acceleration of the vehicle on increasingly inclined road surfaces, whether or not the vehicle is operating in a speed control (cruise control) state has not been addressed.